Optical Characterization of a Ferroelectric Liquid Crystalline Polymer Studied by Time-Resolved Optical Waveguide Spectroscopy

Abstract

The static structures and switching dynamics of a side chain ferroelectric liquid crystalline polymer (PSiOFLC) were investigated by using time-resolved optical waveguide spectroscopy (TROWS). A good alignment of the mesogenic side chains was obtained by a shearing procedure. The liquid crystalline phases of PSiOFLC were characterized by determining the dielectric tensor diagonals of PSiOFLC, in which the contribution of the main chain to the optical anisotropy could be neglected. The PSiOFLC layer in the SA phase could be treated as a uniaxial refractive index ellipsoid which aligned parallel to the substrate plane with bookshelf structure. The PSiOFLC layer in the SC* phase under the large electric field was also considered as a uniaxial ellipsoid model. The transient waveguide mode patterns of PSiOFLC were successfully obtained with a millisecond time resolution. During the reorientation, the smectic layer structure changed from bookshelf to chevron and then back to the bookshelf structure. The slowness of the switching time was attributed to a “polymer effect” in which the polymer backbones lying in the smectic layer plane act as a “hook” to restrict the motion of side chains due to the binding of the mesogenic moieties to the polymer backbone, resulting in the increase of viscosity.

Synthesis and Characterization of New Chiral Side Chain Liquid Crystalline Polyoxetanes

“…[2][3][4][5][6] The FLCs show, in general, fast response times in electric fields; for that reason, they have a potential for electrooptic displays. 2,[7][8][9] In comparison with the FLCs, ferroelectric side-chain liquid crystalline polymers (FSLCPs) [10][11][12][13][14][15][16][17][18] have shortcomings of higher melt viscosity and, thus, longer switching time. Despite these disadvantages, FSLCPs are still attractive materials because their polymeric nature results in better mechanical strength when compared with those of FLCs.…”

“…Since ferroelectricity of the S C * phase was reported by Meyer in 1975, numerous ferroelectric liquid crystalline compounds (FLCs) have been synthesized and characterized. − The FLCs show, in general, fast response times in electric fields; for that reason, they have a potential for electrooptic displays. ,− In comparison with the FLCs, ferroelectric side-chain liquid crystalline polymers (FSLCPs) − have shortcomings of higher melt viscosity and, thus, longer switching time. Despite these disadvantages, FSLCPs are still attractive materials because their polymeric nature results in better mechanical strength when compared with those of FLCs. ,− Furthermore, if the chemical structure of the polymer is properly designed, in other words, if they have a flexible main chain backbone and a sufficient spacer length so that the side group mesogens are efficiently decoupled from the polymer backbone, FSLCPs having fast switching times in the microsecond region can be obtained.…”

Synthesis of Polythiophene Derivatives Bearing Ferroelectric Liquid Crystalline Substituents

“…The chemical structures of the polymers were confirmed by 1 H NMR. 19 F NMR of P2 in CDCl 3 showed a peak at δ ) -186.39, which is assignable to a fluorine atom attached to the chiral center (CF 3 C 6 H 5 as a standard, In the case of compound 6, upon cooling from the melting point of 151 °C, a N* phase with fingerprint texture [26][27][28] was observed at 149 °C, the texture changed into a "shell"-printed texture of chiral smectic C (SmC*) phase at 139 °C, and striated "rose" texture of chiral smectic I (SmI*) phase 29,30 appeared at 96 °C. Finally, compound 6 changed into crystal at 77 °C via the SmJ* phase.…”

“…It is well-known that FLC molecules have the ability to respond more quickly to an electric field used as an external electric field than nonchiral LC ones and that the ferroelectric liquid crystallinity is due to spontaneous polarization generated in the chiral smectic C phase (SmC*) when it is surface stabilized. [18][19][20][21][22] In this study we synthesized novel FLC polythiophene derivatives through introduction of a fluorine-containing chiroptical LC group into the 3-position of the thiophene ring, and we examined the temperature dependence of the dielectric constant in the framework of applications for electronic devices with high-speed response and with the aim of achieving higher structural order through ferroelectric liquid crystallinity.…”

Electro‐optical behavior of ferroelectric liquid crystalline polyphenylene derivatives

“…Ferroelectricity is required to have a spontaneous polarization that is generated by assembly of dipole moments. In the case of LC molecule, the spontaneous polarization is only realized in S C * phase 13. In other word, the S C * phase is responsible for ferroelectricity.…”